The present invention relates generally to lithographic exposure equipment, and more particularly, to a photolithography system and method, such as can be used in the manufacture of semiconductor integrated circuit devices.
In conventional analog photolithography systems, the photographic equipment requires a mask for printing an image onto a subject. The subject may include, for example, a photo resist coated semiconductor substrate for manufacture of integrated circuits, metal substrate for etched lead frame manufacture, conductive plate for printed circuit board manufacture, or the like. A patterned mask or photomask may include, for example, a plurality of lines or structures. During a photolithographic exposure, the subject must be aligned to the mask very accurately using some form of mechanical control and sophisticated alignment mechanism.
U.S. Pat. No. 5,691,541, which is hereby incorporated by reference, describes a digital, reticle-free photolithography system. The digital system employs a pulsed or strobed excimer laser to reflect light off a programmable digital mirror device (DMD) for projecting a component image (e.g., a metal line) onto a substrate. The substrate is mounted on a stage that is moves during the sequence of pulses.
U.S. patent Ser. No. 09/480,796, filed Jan. 10, 2000 and hereby incorporated by reference, discloses another digital photolithography system which projects a moving digital pixel pattern onto specific sites of a subject. A xe2x80x9csitexe2x80x9d may represent a predefined area of the subject that is scanned by the photolithography system with a single pixel element.
Both digital photolithography systems project a pixel-mask pattern onto a subject such as a wafer, printed circuit board, or other medium. The systems provide a series of patterns to a pixel panel, such as a deformable mirror device or a liquid crystal display. The pixel panel provides images consisting of a plurality of pixel elements, corresponding to the provided pattern, that may be projected onto the subject.
Each of the plurality of pixel elements is then simultaneously focused to different sites of the subject. The subject and pixel elements are then moved and the next image is provided responsive to the movement and responsive to the pixel-mask pattern. As a result, light can be projected onto or through the pixel panel to expose the plurality of pixel elements on the subject, and the pixel elements can be moved and altered, according to the pixel-mask pattern, to create contiguous images on the subject.
With reference now to FIG. 1a, a conventional analog photolithography system that uses a photomask can easily and accurately produce an image 10 on a subject 12. The image 10 can have horizontal, vertical, diagonal, and curved components (e.g., metal conductor lines) that are very smooth and of a consistent line width.
Referring also to FIG. 1b, a conventional digital photolithography system that uses a digital mask can also produce an image 14 on a subject 16. Although the image 14 can have horizontal, vertical, diagonal, and curved components, like the analog image 12 of FIG. 1a, some of the components (e.g., the diagonal ones) are neither very smooth nor of a consistent line width.
Certain improvements are desired for digital photolithograph systems, such as the ones described above. For one, it is desirable to provide smooth components, such as diagonal and curved metal lines, like those produced with analog photolithography systems. In addition, it is desired to have a relatively large exposure area, to provide good image resolution, to provide good redundancy, to use a relatively inexpensive incoherent light source, to provide high light energy efficiency, to provide high productivity and resolution, and to be more flexible and reliable.
A technical advance is provided by a novel method and system for making smooth diagonal components with a digital photolithography system. In one embodiment, the method for performing digital lithography exposes a first pixel element onto a first site of a subject such as a resist coated wafer. The method then repositions the wafer for a distance and exposes a second pixel element. The exposure from the second pixel element xe2x80x9coverlays,xe2x80x9d or xe2x80x9coverlapsxe2x80x9d a portion, but not all, of the exposure from the first pixel element. This process can be repeated until a majority of the wafers surface is exposed.
In some embodiments, the method repositions the subject in a different direction and exposes a third pixel element onto the subject. The exposed third pixel element overlays a portion, but not all, of the exposure from the first pixel element and/or the second pixel element.
In some embodiments, the first distance is less than half the length of the first site. After exposing the second pixel element, the system can scan again and expose a third pixel element. The exposure from the third pixel element overlays a portion, but not all, of the exposure from both the first pixel element and the second pixel element.
A system is also provided for making smooth diagonal components. The system includes means, such as a computer, for providing a first digital pattern to a digital pixel panel, such as a deformable mirror device (DMD). The DMD is capable of providing a first plurality of pixel elements for exposure onto a plurality of sites of the subject, each of the sites having a length in one direction and a width in another direction.
After exposure, the subject can be repositioned in the one direction, relative to the digital pixel panel. The DMD is then capable of providing a second digital pattern for exposing the second plurality of pixel elements onto the plurality of sites of the subject. The exposed second plurality of pixel elements overlays the exposure from the first plurality of pixel elements.
An advantage of the present invention is that very smooth and consistent diagonal components (and other shaped components) can be produced with digital lithography.
Another advantage of the present invention is that a high image resolution is maintained.
Yet another advantage of the present invention is that it can provide good redundancy.
Still another advantage of the present invention is that it maintains the same data capacity as conventional digital photolithography systems.